Focal plane shutter for cameras

ABSTRACT

A camera shutter mechanism for opening and closing a shutter aperture to effect an exposure comprises a group of opening blades movable, when released, from a closed position covering the shutter aperture to an open position uncovering the shutter aperture to thereby initiate an exposure, and a group of closing blades movable, when released, from an open position uncovering the shutter aperture to a closed position covering the shutter aperture to thereby terminate the exposure. A release mechanism releases the opening blades thereby enabling them to move to the open position for initiating the exposure, and subsequently releases the closing blades thereby enabling them to move to the closed position for terminating the exposure. A driving member automatically operates immediately after completion of the exposure to move the group of opening blades back towards the closed position so that the aperture is at least partially covered thereby so as to improve the light-shielding capability of the shutter mechanism.

RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.686,501 filed May 14, 1976, now abandoned.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a shutter blade arrangement of a focal planeshutter for cameras.

In the conventional, so-called metal focal plane shutter which opens orcloses an aperture by displacing a plurality of divided shutter bladesto different extents of displacement one after another, the size of suchdivided blades in general tends to be large because of the large area ofthe aperture. This in turn tends to call for a larger shutter space,which is not suitable for a compact camera. Particularly, in cases wheresuch a metal focal plane shutter is employed in the so-calledsingle-lens reflex camera which is arranged to observe an image througha photographing lens at a view finder disposed on top of the camera bodyand which has become popular in recent years, the shutter blades whichare folded or retracted in the upper part of the camera during anexposure operation are positioned immediately below the finder; and thisrestricts the finder mounting position in the vertical direction thuspresenting a problem in the reduction of the size of the camera.

Generally, the size of this type of single-lens reflex camera in thevertical direction is determined by the size of a film loading chamberor a lens barrel in the lower part while it is determined by theposition of a pentagonal prism or the view finder in the upper part ofthe camera. The size in the lower part of the camera can be set at arelatively large value because of the relatively large space availablethere. As for the size in the upper part of the camera, however, it isthe most difficult problem, achieving reduction in the size of thecamera, to make smaller the space required for stowing the foldedshutter blades between the shutter aperture and the view finder. Thishas indeed been the most serious drawback of the focal plane shutter ofthe type that moves the divided shutter blades up and down as comparedwith another type of focal plane shutter that operates a cloth screenarrangement in the transverse direction.

One conceivable method for solving this problem is to minimize the bladestowing space by further dividing the divided shutter blades. Inaccordance with such a method, however, the light shieldingeffectiveness of the shutter degrades as the number of such dividedblade increases.

This invention, therefore, is directed to the provision of a focal planeshutter which eliminates the above mentioned drawback of theconventional shutter without lowering the light shielding ability andwhich is suitable for compact cameras. In accordance with thisinvention, a focal plane shutter of the type that accomplishes exposureby causing a plurality of divided shutter blades to run from the upperpart of the camera to the lower part thereof comprises a group ofopening blades which are divided blades excelling in light shieldingeffectiveness being prepared into a lesser number of divisions orarranged to overlap one another to an ample degree when they are in astate of covering the shutter aperture, this group of opening bladesbeing arranged to be stowed in a space provided in the lower part of thecamera; and another group consisting of closing blades which areprepared into smaller sized divisions or arranged to overlap one anotherto a lesser degree when they are in a state of covering the aperture,the latter group of shutter blades being arranged to be stowed in theupper part of the camera requiring only a small space there althoughthey are inferior in light shielding effectiveness. Upon completion ofan exposure, the aperture is covered by the less light effectiveshielding group of closing blades only for a predetermined brief periodof time. Then, when the predetermined period of time has passed, thegroups of the opening and closing shutter blades are displacedapproximately into a charged position in such a manner that the apertureis constantly covered by the group of opening blades which excel inlight shielding effectiveness. By such arrangement, the space requiredin the upper part of the camera for stowing the group of closing bladeswhich are to be folded there can be made smaller without impairing thelight shielding effectiveness of the shutter. Such a focal plane shuttermakes possible further reduction in camera size. Furthermore, uponcompletion of the exposure operation, only the group of closing bladeswhich have accomplished their work are displaced in the chargingdirection within a predetermined short period of time in such a manneras to additionally cover the aperture which has already been covered bythe group of closing blades, so that the reduction in the space requiredfor stowing the group of closing blades which are to be folded in theupper part of the camera can be made possible without impairing thelight shielding effectiveness of the shutter.

Therefore, compared with the conventional focal plane shutter of thetype arranged to accomplish exposure by running a plurality of dividedshutter blades in the vertical direction, the shutter constructed inaccordance with this invention makes it possible to manufacture muchsmaller cameras. Then, as compared with the other type of focal planeshutter which is arranged to accomplish exposure by transversely runninga cloth screen, the shutter of the present invention still permits thesame degree of reduction in the size of the cameras. The inventivecamera shutter, therefore, has a great advantage.

Further features and advantages of the present invention will best beunderstood from the following detailed description when read inconnection with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates the locations of focal plane shutters, FIG. 1(A)showing the location of the conventional shutter;

FIG. 1(B) that of the invented shutter and

FIG. 1(C) being a side view of FIG. 1(B).

FIGS. 2 through 5 illustrate an embodiment of this invention with

FIG. 2 being a plan view showing the shutter in a charged state.

FIG. 3 a plan view showing the shutter in an open state;

FIG. 4 a plan view showing the shutter in a state immediately aftercompletion of exposure and

FIG. 5 another plan view showing the shutter in a state of havingcompleted a series of actions.

FIG. 6 is a partial plan view of a second embodiment of the inventionshowing the essential part of the shutter in a state of having beencharged.

FIG. 7 is another partial plan view illustrating a third embodiment ofthe invention and showing the essential part of the shutter in a stateof having been charged.

FIG. 8 is a plan view of a fourth embodiment of the invention showingthe shutter in a state of having been charged.

FIG. 9 is another plan view of a fifth embodiment of the invention in astate of having completed a series of actions.

FIGS. 10 and 11 are plan views both illustrating a sixth embodiment ofthe invention,

FIG. 10 showing it in a charged state and FIG. 11 showing it in a stateof having completed a series of actions.

FIG. 12 is a plan view of a seventh embodiment of the invention showingit in a state or having completed a series of actions.

Referring to FIG. 1 which illustrates the location of the focal planeshutter in a single-lens reflex camera,. FIG. 1(A) represents theconventional shutter location having a view finder a disposed above theshutter b. FIG. 1(B) represents the shutter location of the presentinvention and FIG. 1(C) is a side view of the invented shutter. As shownin FIG. 1(C), there are provided a reflecting mirror c and a lens barrele in front of the shutter b while there is located a film d in the rearof the shutter. Above the shutter, there are located a pentagonal prismf and a view finder a.

In FIG. 2 which illustrates the first embodiment of this inventionshowing the shutter in a state of having been charged, there is formedan aperture 1a in a base plate 1 for the purpose of exposing the film.In a cover plate 2 which provides a space for operating the shutterblades to open and close the aperture 1a in the film exposing operation,there is provided another aperture 2a which coincides with the otheraperture 1a, the cover plate being of about the same shape as the baseplate 1. The cover plate is carried by the base plate 1 in an ordinaryknown manner, which is not illustrated and which is omitted fromdescription for simplification. An opening blade group 3 consists of 4opening blades for opening the aperture 1a to effect exposure andincludes an opening slit type blade 3a and shielding blades 3b, 3c and3d. The opening slit type blade 3a is pivotally held by an opening arm 4and an auxiliary opening arm 5 at shifts 4a and 5a on their reversesides in such a manner as to make a parallel movement utilizing thenature of a parallelogram, the arms 4 and 5 being rotatably held atshafts 4e and 5e on the base plate 1 respectively. The shielding blades3b and 3c and 3d are held to be rotatably coaxially with the shaft 5a ofthe auxiliary opening arm 5. On the other hand, the slots 3b', 3c' and3d' are respectively formed in these shielding blades 3b, 3c and 3drespectively and a pin 4f which protrudes from the middle part on thereverse side of the opening arm 4 is inserted through these slotsrespectively. A closing blade group 6 of closing blades which closes theaperture 1a upon completion of exposure comprises 5 blades including aclosing slit forming blade 6a and closing blades 6b, 6c, 6d and 6e. Theclosing slit forming blade 6a is held, virtually in the same manner asthe opening blade group 3, by a closing arm 7 and an auxiliary closingarm 8 on their surfaces at shafts 7a and 8a, these arms 7 and 8 beingrotatably held at shafts 7e and 8e on the base plate 1 respectively. Theclosing blades 6b, 6c, 6d and 6e are held to be rotatable coaxially withthe shaft 8e. A pin 7f which is provided in the middle part of theclosing arm 7 to protrude from the surface thereof is inserted into theslots 6b', 6c', 6d' and 6e' which are provided in these closing blades6b, 6c, 6d and 6e respectively.

When the aperture 1a has been opened, the opening blade group 3 and theclosing blade group 6 are respectively folded or retracted into spacesprovided in the lower and upper parts of the camera. Then, the size ofthe closing blade group 6 in a folded or retracted state in the upperpart is arranged to be smaller than that of the opening blade group 3,also in a folded or retracted state in the lower part. A driving member9 comprises arms 9c and 9d which respectively engage pins 4g and 7gprotruding from the middle parts of the opening and closing arms 4 and7; a side edge portion 9e which is provided for locking; and two slots9g. The driving member 9 is mounted for sliding movement in the upperand lower directions on two shafts 9a, with two slots 9g serving asguides; while a spring 9f constantly urges the member 9 upward. A hookmember 10 comprises a claw 10b which serves to lock the driving member9, and an arm 10c which engages a curved portion 8h of the auxiliaryclosing arm 8. A rightward turning spring (not illustrated) is disposedto be rotatable on a shaft 10a to bias the hook member in the rightwardor clockwise direction.

The focal plane shutter described in the foregoing operates as follows:With the shutter under the charged condition as illustrated in FIG. 2,when a release button of the camera is depressed to release the shutterby a known method, the opening arm 4 is unlocked (not illustrated) and aspring (not shown) causes the arm 4 to swing clockwise. Then, the linkmechanism arranged in the nature of parallelogram causes the openingslit forming blade 3a to run in a parallel manner downward over theaperture 1a. Concurrently with this each of the shielding blades 3b, 3c,and 3d rotates through an angle corresponding to the slot providedtherein, on the shaft 5e with the rotation being aided by the pin 4fwhich is inserted in the slots 3b', 3c' and 3d' of these blades. In thismanner, the opening blade group 3 opens the aperture 1a and this resultsin a condition as illustrated in FIG. 3. After the release of theopening blade group 3, when the time of exposure set by known means haselapsed, the closing arm 7 is released from locking means (notillustrated) and begins to swing clockwise due to the force of anunillustrated spring. Then, the link mechanism arranged in the nature ofa parallelogram causes the closing slit forming blade 6a to run downwardas viewed in the drawing over the aperture 1a in a parallel manner;while the pin 4f which is inserted through each of the slots 6b', 6c'and 6d' of the shielding blades 6b, 6c and 6d causes these shieldingblades to rotate on the shaft 8e through angles corresponding to theslots respectively. The closing blade group thus closes the aperture 1ato complete the exposure and bring about a condition as illustrated inFIG. 4.

In FIG. 4 which illustrates the condition immediately after completionof exposure, the driving member 9 is unlocked with the hook member 10having been turned counterclockwise by the curved portion 8h under thiscondition. Further referring to this drawing, when the driving member 9which has been unlocked is moved upward by the spring 9f, the arms 9cand 9d which are provided on the driving member 9 engage with and pushthe pins 4g and 7g which are protruding from the opening and closingarms 4 and 7 to move the groups 3 and 6 of opening and closing bladesapproximately into their charged positions. This brings about acondition as illustrated in FIG. 5 showing that a series of actions havebeen completed.

Referring now to FIG. 5, the shutter is charged in the following manner:After the opening and closing arms 4 and 7 have been brought into lockedpositions by known means (not shown) against the force of anunillustrated spring arrangement, the driving member 9 is pusheddownward against the spring 9f by a known method to lock it by means ofthe hook member 10. This results in the condition as illustrated in FIG.2.

The second embodiment of this invention is illustrated in FIG. 6, whichis a plan view showing the essential parts under a charged condition.Unlike the first embodiment, the opening and closing blade groups 3 and6, after completion of their exposing actions, are moved in the chargingdirections in response to engagement with a curved part 207h of aclosing arm 207 instead of the curved part 8h of the first embodiment.In FIG. 6, the parts which are virtually the same as the correspondingparts of the first embodiment are indicated by like reference numeralswhile the parts which are modified from the corresponding parts of thefirst embodiment are indicated by adding 200 to the reference numeralsused in the first embodiment, so that they can be understood withoutrepeated description.

FIG. 7 is a plan view of the third embodiment showing the essentialparts thereof under a charged condition. Unlike the first embodiment,the opening and closing groups 3 and 6 of blades, which have completedtheir exposing actions, are arranged to move not in response to thecurved part 8h of the first embodiment but in response to engagementwith an operating member 11 which operates in the direction of the arrowin relation to the movement of a reflecting mirror back to the imagereflecting position thereof.

FIG. 8 is a plan view of the fourth embodiment of this invention showingthe shutter under a charged condition. This embodiment differs from thefirst embodiment as follows: The opening blade group 403 and the closingblade group 406 respectively consist of two opening blades 403a and 403band two closing blades 406a and 406b which are held at shafts 4a, 5a,4b, 5b, 7a, 8a, 7b and 8b to form a link mechanism which enables thesegroups of blades to make parallel movements utilizing the nature of aparallelogram respectively. In opening the aperture 1a, the group 403 ofopening blades and the group 406 of closing blades are folded orretracted to be stowed in the lower and upper parts of the camerarespectively. The size of the closing blade group 406 when retracted andstowed in the upper part is arranged to be smaller than that of theopening blade group 403 when retracted and stowed in the lower part ofthe camera in the same manner as in the first embodiment. Thus, underthe condition of covering the aperture 1a, the light shielding effect ofthe closing blade group 406 is inferior to that of the opening bladegroup 403 also in the same manner as the first embodiment. Furthermore,the parts which are virtually the same as the corresponding parts of thefirst embodiment are indicated by like reference numerals while theparts which are modified from the corresponding parts of the firstembodiment are indicated by adding 400 to the reference numerals used inthe illustration of the first embodiment, so that they can be understoodwithout repeating the same description.

FIG. 9 is a plan view of the fifth embodiment of this invention showingit in a state of having completed of series of actions, this statecorresponding to the state shown in FIG. 5 which illustrates the firstembodiment. This embodiment differs from the first embodiment asfollows: To shorten the operating stroke of the driving member 9required for displacing the opening and closing groups 3 and 6 of bladesin the changing direction, there is added a stop pin 12 which permitsmoving the closing blade grouup 6 up to a folded or retracted positionwhere a sufficient light shielding effect can be obtained and alsopermits moving the opening blade group 3 up to a point where this groupoverlaps the closing blade group 6 thereby giving a sufficient lightshielding effect. More specifically stated, when an aperture is coveredby a shutter arrangement consisting of a plurality of divided blades,the light shielding effect of the shutter blades increases as they movefrom their full aperture covering positions toward their foldingpositions or, in other words, as they overlap each other to a greaterdegree. This advantage of divided shutter blades is further utilized inthe fifth embodiment by minimizing the operating stroke of the drivingmember 9, so that the size of the shutter can be more advantageouslymade smaller. In charging the shutter, either the opening and closingarms 4 and 7 or the auxiliary closing arms 5 and 8 are turnedcounterclockwise against the force of an unillustrated spring to belocked by unillustrated known means; and the driving member 9 is pusheddownward against the spring 9f by a known method to lock it with thehook member 10. The shutter operates virtually in the same manner as inthe first embodiment.

FIGS. 10 and 11 are plan views of the sixth embodiment of thisinvention. FIG. 10 illustrates the shutter in a state of having beencharged while FIG. 11 illustrates it in a state of having completed aseries of actions. In these drawings, like reference numerals indicatelike parts as compared with the preceding embodiment with the exceptionthat the parts modified in this example are indicated by adding 600 tothe applicable reference numerals to make them self-explanatory.

Next, the operation of the shutter is as follows: With the shutter underthe charged condition as shown in FIG. 10, the shutter is released by aknown method when a release button of the camera is depressed. Theopening arm 4 which has been locked by unillustrated means is therebyunlocked and begins to swing clockwise due to the force of anunillustrated spring. The link mechanism which is arranged utilizing thenature of a parallelogram causes the opening slit forming blade 3a torun downward parallel with and over the aperture. Concurrently withthis, the pin 4f which protrudes from the opening arm 4 and is insertedin the slots 3b', 3c' and 3d of the shielding blades 3b, 3c and 3dcauses these shielding blades to turn on the shaft 5e through anglescorresponding to their respective slots. Thus, the aperture 1a is openedby the opening blade group 3. After the release of the opening bladegroup 3, when the exposure time as set by known means has elapsed andthe closing arm 207 is released from unillustrated locking means, theclosing arm is caused to begin a clockwise turn. Then, the link which isarranged utilizing the nature of a parallelogram causes the closing slitforming blade 6a to run downward over the aperture 1a in paralleltherewith. Concurrently with this, the pin 7f which protrudes from theclosing arm 207 and is inserted in the slots 6b', 6c', 6d' and 6e' ofthe shielding blades 6b, 6c, 6d and 6e causes these shielding blades toturn on the shaft 8e through angles corresponding to their respectiveslots. The closing blade group 6 thus closes the aperture 1a to completethe exposure.

In the region where the closing blade group 6 completes the exposureaction, the curved part 207h of the closing arm 207 causes the hookmember 10 to turn counterclockwise and the driving member 609 isunlocked accordingly. The force of the spring 9f then causes theunlocked driving member 609 to move upward. This in turn causes the arm9c provided on the driving member 609 to push the pin 4f protruding fromthe opening arm 4; and the opening blade group 3 is displaced therebyapproximately into a charged position to complete a series of actionsand this results in the condition as illustrated in FIG. 11.

In charging the shutter, either the opening and closing arms 4 and 207or the auxiliary opening and closing arms 5 and 208 are caused to turncounterclockwise from the condition illustrated in FIG. 11 against theforce of an unillustrated spring and are locked by unillustrated means.At the same time, the driving member 609 is pushed downward by a knownmethod and is locked by the hook member 10 as shown in FIG. 10.

FIG. 12 is a plan view of the seventh embodiment of this inventionillustrating it in a state of having completed a series of actions (acondition corresponding to that of the sixth embodiment as illustratedin FIG. 11). To shorten the operating stroke of the driving member 609required for displacing the opening blade group 3 in the chargingdirection after completion of an exposure, there is added a stop pin 12.In other words, in cases where an aperture which has already beencovered by a group of closing blades is to be additionally covered by agroup of opening blades, the purpose can be attained by moving the groupof opening blades to cover just a range where the light shielding effectof the group of closing blades is insufficient. Accordingly, in thisexample, the operating stroke of the driving member 609 is limited tosuch a range to permit further reduction in the size of the shutter. Theshutter in this embodiment operates virtually in the same manner as inthe sixth embodiment.

The foregoing description of the embodiment of this invention has beenmade on the assumption that the shutter is employed in a single-lensreflex camera. However, this invention is not so limited and it is to beunderstood that the invention may be practiced in exactly the samemanner in other types of cameras such as a camera equipped with a rangefinder. Furthermore, while the driving member 9 or 609 is employed inthe foregoing description of the preferred embodiments for displacingthe opening and closing blade groups in the charging direction aftercompletion of an exposure, other types of members such as a member whichoperates in relation to the movement of a reflecting mirror back to animage reflecting position may be employed in place of the drivingmember; or some essential component of the camera, such as a reflectingmirror, may be arranged to directly or indirectly move the opening bladegroup up to a preset position. As for the signal required for displacingthe opening and closing blade groups in the charging direction aftercompletion of an exposure, many modifications are possible other thanthose arrangements employed in the foregoing embodiments. Suchmodifications include, for example, an arrangement to give the signal bythe return stroke of the release; the use of a delaying device forgiving the signal at a preset period of time after the displacement ofthe opening blade group has commenced; etc.

With the divided shutter blades arranged as described in the preferredembodiments of this invention, the inconstancy of exposure thatotherwise tends to be caused by the frictional resistance between theclosing blades, the effect of the inertial mass, etc. is eliminated toenhance the precision of exposure.

When this invention is applied to focal plane shutters of the typecomposed of cloth screens, titanium screens, or the like, therestrictions imposed on the material, thickness and/or shape to ensurethe light shielding effect can be eased to give advantages in termsimprovement in performance or reduction in cost.

What is claimed is:
 1. A camera shutter mechanism .Iadd.for a camerahaving a view finder.Iaddend.for opening and closing a shutter apertureto effect an exposure comprising: .Iadd.a base plate having therein ashutter aperture, the base plate having a vertical height dimension anda horizontal width dimension and having a widthwise extending recess atthe upper part thereof at a location vertically above the shutteraperture, the recess being dimensioned to accommodate therein the lowerpart of the view finder;.Iaddend.a group of opening blades movable, whenreleased, from a closed .Iadd.charged.Iaddend.position in which theycover the shutter aperture to an open position in which they do notcover the shutter aperture to initiate an exposure.Iadd., said group ofopening blades being arranged to be stowed in a space provided in thelower part of the camera;.Iaddend.a group of closing blades movable,when released, from an open .Iadd.charged.Iaddend.position in which theydo not cover the shutter aperture to a closed position in .[.with.]..Iadd.which .Iaddend.they cover the shutter aperture to terminate theexposure.Iadd. , said group of closing blades being arranged to bestowed in a space provided in the upper part of the camera beneath theview finder such that the stowed closing blades do not obstruct theoptical path of the view finder; said group of opening blades havingbetter light-shielding effectiveness than said group of closing bladeswhen in the closed position;.Iaddend.release means for releasing theopening blades thereby enabling them to move to the open position forinitiating the exposure, and for subsequently releasing the closingblades thereby enabling them to move to the closed position forterminating the exposure; and means including a driving memberautomatically operable immediately after completion of the exposure formoving the group of opening blades back towards the closed position sothat the aperture is at least partially covered thereby .Iadd.so thatafter termination of the exposure, though before charging of theshutter, the aperture is at least partially covered by the opening bladegroup which has better light-shielding effectiveness than the closingblade group.Iaddend..
 2. A camera shutter mechanism as defined in claim1; wherein said last-mentioned means comprises means for effecting atleast partial covering of the shutter aperture by said group of openingblades within a predetermined period of time after completion of theexposure.
 3. A camera shutter mechanism as defined in claim 1; whereinsaid last-mentioned means comprises means for displacing at least one ofsaid groups of opening and closing blades in the shutter chargingdirection to an extent such that the opening and closing bladessufficiently overlap one another to attain a good light-shielding effectwithin a predetermined period of time after completion of the exposure.4. A camera shutter mechanism as defined in claim 3; wherein saidlast-mentioned means comprises means for applying sufficient drivingforce to said driving member to displace said group of closing bladesand/or said group of opening blades in the shutter charging directionwithin a predetermined period of time after completion of the exposure.5. A camera shutter mechanism as defined in claim 4; including a hookmember operable to hold said driving member under a charged condition.6. A camera shutter mechanism as defined in claim 5; further including aclosing arm having a curved portion engageable with said driving memberto effect actuation thereof.
 7. A camera shutter mechanism as defined inclaim 1; wherein said group of closing blades is composed of dividedblades which can be stowed in a space smaller than the space requiredfor stowing said group of opening blades.
 8. A camera shutter mechanismas defined in claim 7; wherein said group of closing blades is composedof a greater number of divided blades than the number of divided bladesof said group of opening blades.